Defective needle spotter



28, 1956 DE WITT T. VAN ALEN EI'AL 2,760,363

DEFECTIVE NEEDLE SPOTTER Filed July so. 1951 ?l24 IZI H .9 1, I33

GM 0 ms 325 I INVENTORS. DE WITT 1'. VAN ALEN IOTI-IF'; IIO i BYROBERT W.KORDATZKY 08 l ATTORNEY United States Patent G DEFEC'IHCE'NEEDLE SHUTTER;,-

De Witt T. Van Alen and Robert W. Kordatzky, Dlavan,

wisqeassignors: tooTlie .Gebrge s-Borg: Corporation, Chicago,- -lll.,--.a :COI'PQIflfiOD: of Delaware e- Application July 3011951, Serial Nb. 2393662 =Claims.:: (Cl. 66*91-57fi';

The present invention relates ingeneralto kn'ittingmahchines and the object of the inention .is to .provide.:a defective needle'spottenwhich is adapted to continuously; test theneedle's as knitting proceeds and give. a Warning signal or stop the machine,rorcbothgwhneverethe test-H; ing operation reveals a defective. needle;

In '-.further explanation of thelobjet vof fhelinvention it maybe stated that it was designed 'especiallifonnse with" a pile fabric knitting machine which comprisesa circular latch needle machine such rasmanufactured by'the Wildman MfgQCo'mpany Of"N0i'1iS0WI1,TP3:, Q-D .dni a carding head of the. type whichis' disclosed. 'inlthi pending application of Brandt, Ser. N02 150,447; 'filfedn; M'a'rchfl 11950Inow Patent No.1 2,7105252 eTh'rcardrI ing'head takes up fibrous material,suppliedihith foi mu. of a' sliver orroving and feeds'the' material'tothe needlesiim oftheiknitting machine While the machine is knitting a ba'setabric, whereby" the fibrous materialiis incorporated in the stitchesnfithe base fabric and forms;a pile'ion one. 7 sidelthereoii Theremay bea pluralityof cardin'g heads, usually-four, which'correspond. toand immediately; precedethe samenumber of knitting stations, respqca tively.

Each cardin'gheadis mounted on the frame .of the; knitting machine withthe feeding card;.'c1is'pqsed above and outside but-overlapping the circular'row'of ueedles;. The operationoftransferring the..fibrous material from the 'feeding card to"the, needles-is carriedout bYraisin'g yr the needles-vertically as: they approach; the card; so that as the needles pass alohgthevrotating card they penetrate" into" the card-clothing and the fibrous material thereon and become filled with fibers-"which catch-on-th hooks of *the-needles'and are pu-lledoutjof-themass-of'fibersi r on' 'the-cardz Dtiringthis operation themeedle's'artdsth" cardclothing encounteredthrebyaremoving indifieren 7 directions and although/the peripheral speed of the'ward' is much higher-than that of -the-need1e-cylinder andtth '50 teeth of'the card 'are'quitefiekible the needles-aresub jected to severe punishment as -the'y';pass 'through each carding head;

In consequenceof thefor'egoing a considerable amount-* of needle wear and somebreaka'ge take'splacer Pennynently 'closed 01""S1Il1Ck" latches are anothe'r source-"0F trouble. A stuck latchis a latch"whiehhas'beerrsprung past the end of the-hook and has assumed 'a position" inside the hook,- making it inipossibleforthe latchto open; A needle' whi'ch'is defective-either=because'-ef a '60 broken hook or a stuck latch'dropsgstitche's andprodu'ces a run in th knitted base --fabrici It "is desirable"there fortQfind and replace such 'defetive needlesas soonas possible. 7

According to' the oi-men practice; defectiv needlswere detected :by watching for runs asathe knitted base fabric emerged beneath the'needle'cylinder. I As soon as a run was seen the operatorstopped the machii1e and replaced theadefectiveneedle;:. Since-.110 :run would: be ie seen zuntilithe starting end.:of-:it appeared beneath: thesescylinden revery run gwvonldrinevitablyr be ;-;4 mrz j inchfiser long before it was observed and the defective needle 2,760,363 Patented Aug 28,; 1

ice

2.2 replabedfi Longer trunsrcouldaoccuraif theroperatorobae' came inattentive torv occupied temporarily,;witht repaizsi s on anothelnmachine, I A115 "such 1'UI1S. -COl1Stiil1t&z-de\fCCtS.;s inlthe; knitted baseiabric and,had..to. be repaired byze; hand.

The present invention :solvesthe.problemi.outlined: in the'foregoing by providing what. wecalLa defective-needle, spotter, which isadapted to detect a defective. needle prpmptly'when it becomesdefective andimmediatelyistop the machine. Thecomplete spotter includes a mechani==.- cal and electromagnetic, pickup device mountedonrlhe'se frame of the knitting machineiadjacentlhenpatheof the needles asthey pass by, ,togethe'r withan electronieIcon-i. trol. circuit it installed .in' a suitabIe'cabinet .or containenadjacent lithe machine and cooperating )vithjhe'. pickup; device-in response to.signals produceditherehy to. either signalthe operator orrstop the' machine. For reasons;. explained it .Will usually be preferable .to stop themachine instantly as-soon as'the' defective needle is discovered- Thei'invention Will' be more fully described in: the; ensuing specification, reference being had to the accom-spanyjng drawing, in which- Fig; '1 is artop' or; plan rview of'th'e' pickup device as itappears when mounted 'on the. sinker cam .nng pf 21 knitting machine; v

Fig-'32 is'a sectiohon the iirie;2-i2,fFig'.1. 1,showing thet'partst'includedin the magnetic pickup circuit, in clu'ding one ofithe neediesbf-the knitting machine;

Fig.5 is'a section'on thelirie 3- 3, Fig. 1, showing b the feeler memberfordetecting needles havin'gg stuckf latches; V v

P1255 4 isa view--of-th pickup deviceasseen'fremihei bottom; or after it -isrotated' 1 from'ithe position. in; whi'ch'it is shown inFigfl; r

Fis -5 and 6 are-partialyiews ofa stuck latch needle" and a broken-needle; respectively; and i Fig; :7 is a diagrammatic -'circuit drawing;

Referring now tol ig's. l to' 4, inclusive-,- the reference character *10 indicates-a part of: the" needle cylindermf" the'km'tting'machine, -whilereference character 11 indi G cateswa part-of the sinker-cam ring: Theseparts'are? shown in section in Fig: ;2, Since-theknitting" machine is Well krikJWrtna considerable amount -of'detail hasbeen'" omitted=- in order not to complicate'the "drawing In FigS -l a row of-needies -12 is shownbut-the-interspersed f sinkers have' beenleftout. In 'EiQrZ the sinker 14 is s shown, also a needle 12, but the needles-and'sinkersback' of'the' 'section lin'ehavebeen omitted. 1 FigSQ also'shows the' sinke'rasupportin'g ring' 15; 'whi'ch' surrounds the cylin der lfland-is supported on-a plurality of gronpsoffins suclr as 16 ivhichproject-"frorn theperiphery of thcyk indei'sa' The various parts of-the pickup device are mounted on the -base="20 =which preferably is i a "castingof -some-anonmagnetio 'metal such as brass or-- aluminum. Thiscasting is about 3 inches square and /z'dnch'thi'ck and has-a number-of recesses andwpenings as shoWn-im-the drawing. It is mountedon thetop of the'sinker carn ring 11 by' rneans 'of 'screws-'21'"and -22 "as shownin i fig 'gl.

The -base -20" overlaps "the needle'" cylinder 10 and tias The-curvedfinger :Stbis :secured: to: thev lowers-skier.ofa'e the base 20 by means of a screw 31, as shown in Figs. 1

' finger projects 35 .and 36 to the upper end of magnet 33.

forward in the direction from which the needles approach the pickup device andhas'a curved loweredge'which functions to depress andopen any needle latch which may'happen to bc'p rtly closed. The finger 30 thus insures that when each needle passes .beneaththeipickup device its latch'will be in open 'posi-' tion as shown in the case of latch" 13 of needle 12 in a 7' needles suchas the needle shown in Fig. 5. a

' ,The reference character '33- indicates a permanent mag net, preferably of alnico, and 34 indicates a pole piece .made preferably of 'a thin steel lamination. These parts are clamped between the two clamping bars 35 and 36- ,by means of'the screws 37 and 38 as shown in Fig. 1,

the'clamping bars having suitable recesses at the left hand end to receive the magnet'33.. The clamping bars arernade of some suitable magnetic material such as cold rolled steelf In" order to' mount'this assembly on the base 20 Ia slot 60, Fig. 4, is sawed from the left'hand end of' the base clear through to the "opening 23, the slot being substantially equal in width to the thickness of the pole piece 34. The slot is enlarged at the left by milling or other operation to receive the lower end' of 2,7eo,ses I 54 bears on the part 56onithejopposite side thereof from 7 Fig. 2. This does not'apply of course to stuck latch inFig.4.' I i The feeler member 52 whichv is described above: insulated from the frame at all points but is conductively 3 fof resilient wire havingone end'inserted in a hole the wall of recess 50 and having the other end bearing.

against the part 56, the'wire being bent at the grooved nut153 which serves as a fulcrum to enable the spring a a to exert pressure against 56. The springis insulated from' 3 v a bushing 59, indicated'byfdotted lines the frame by connected to the screw 47 through the nut 53, andthe screw 47 is connectedby. means of the strap 46' to the i terminal set which includes the terminal 45. This terminal is grounded whenever a needle having a stuck latchpasses the detecting device. ,For this purpose thepivoted feeler member 52' is provided with an offset extension 55. a I for contacting stuck latches; 'As seen in-Fig. 3;-a needle having an open latch'such as the needlepartly shown in' f this figure can pass theextension 55 withoutcontacting the magnet; After the magnet assembly is lowered into its proper position on the base 20 as shown in Fig.2 it is secured in position by means of the screw 39 which clamps together those parts of the base which are on: opposite sides of the slot. ,7

When the complete pickup device'is mounted on the sinker cam ring lllthe lower end of'magnet 33 should rest on the ring, to avoid any air gap at this point- To insure thatit does so the screw 39 may be loosened and V Qthemagnetpressed down firmlyagainst the ring after which the screw may be tightened up again. The sinker cam ring 11, thesinker ring, the sinkers, and the needle cylinder'a're all made of steel 'so that a magnetic circuit is established which extends from thelower end of magnet a a 33 by way of the sinker cam' ring and the sinker ring' and associated parts'to the needle 12, for example, Fig. ,2,

and thence by way of the pole piece 34 and clamping bars There is necessarilyasmall air gap between the hook of the needle 12 and the tip .of the pole piece 34, so that needle 12 and other needles can pass freely past thepole piece.

The air gap can be adjusted by means of the member 24. This member, made of nonmagnetic maj and 44 of the coil of this tube.

terial, aligns the needlesaccurately and insures so far .as possible that the air gap will be the same for each needle, except of course in the case of a broken needle such as shown in Fig. 6.

The reference character 40 indicates a coil of conventional'construcfion, whichsurrounds the pole piece 34 a and is provided with terminals which aresecured'beneath binding posts on the terminalstrip 41. This terminal strip may be'of any suitable construction, but preferably has four sets of terminals (only three are required for the electrical connections) so that an ordinary machine screw 42 can be used to secure the terminal strip to the base 20.

Referring now particularly to Figs. 3 and 4, the are V rangement'for detecting a stuck latch will be described.

it, but in the case of 'a needle having a stuck 'latch as shown in Fig. Sthe latchiwill engage extension and ground terminal 45 as set forth. When engaged .by a stuck latch .the member 52 rotates on its pivot slightly 7 against the tension of spring 54 so as to let the needle s by- Referring driving one of the carding heads of the knitting machine.

Each carding head has its individual driving moto'rand ,f a the carding :heads work' in parallel to drivethe knitting machine.' 104. designates the operating magnet and an electromagnetic starting switch which connects the motorf100and other. motors on the same'machine to the phase line comprising conductors 101, 102, i and 103 and f I labeled AG in the drawing. TheswitchS is a'manually p operated starting switch. Relays 106 and;109'may:be i

any suitable type of relay, suchas ordinary telephone relays.

.The'tube 115- may be a type ssn pentode and is The :terminals' 43 adapted to operate as an amplifier.

40 are connected to the grid circuit Thetubes 116 and 117 may be type 615 triodes or they may be thetwo halves of a type 6SN7 twin triode. The

function of these tubes will be explainedpresently.

Direct current for the various tube circuits maybe supplied by means of a rectifier (not shown) connected to the positive and negative conductors 121 and 122. A bridge across these conductors includes the resistors 124 and 125,'potentiometer 126, and resistor 127. The voltage regulator tube 119, which is connected in parallel with that portion of the bridge which includes 125,126, and 127, maintains a substantially constant potential between conductors 122 and 128 .which may be for ex- Thisarrangement comprises a pivoted feeler member 52 which is'mounted in the recess 50 on the under side of j the base 20. The pivoted mounting for member 52 comprises a screw 47 and a nut 53 having a short round shank on whichthe member 52 is rotatable. The screw r 47 and nut 53 are'insulatedfrom the base 20 by means of an insulating washer 48, an insulating tube 49,, and

a sheet of insulating material 51, which lines the recess 50. A downwardly projecting part56 formed integrally with member 52 cooperates with the adjusting'screw 58 1 to limit the rotation of member 52 in a clockwise direc-;

" tion as seen in Fig. .4. The part56is insulated fromthe screw 58 in any suitable manner,- as by, means of .7

an interposed sheet of insulating material 57. 7 A spring ample, volts.

The grounded conductor 123 'is connected to theijunction of resistor 125 and potenti ometer 126. The resistance of resistor 125 is preferably the same as that of the potentiometer 126 and resistor 127 together, so that conductor 123 is approximately 52.5

volts positive with respect to conductor; 12 2.

'The-tube 120 maybe a'type' 2050 'Ihyratrontuhei The plate circuitof the tube includes the relay 109 The control grid of the tube is connected 'to the grounded conductor123'by a condenser 131, the capacity of which maybe .029 mf. The resistor 130 is connected in paral lel'with the condenser 131 and may have a valueof 250 M ohms. The cathode of. the tube is connected to the slider of the potentiometer 126, which is used to. adjust the grid bias at; the tube. The potential at the cathode may be; for" example, "about 2 8 volts'negative with respect to ground: The grid'is at ground potential when there is no input signal, so that the tube has a positive "bias 'andfires' when supplied with plate volb' now to Fig.. 7,'the reference character represents a three phasemotor which is the motor for age.. Atubeiofthis type' will fire'if' it has: less than-'- about 2 volts negative 1 grid bias.

The input circuit: over which tube 120' 'is controlled includes the condenser 137, conductor 132, and the: tube 118, which may be half of a 6H6 twin diode, or similar The rectifiers 133 and 134 may be any suitable type of copper oxide or' selenium rectifier, as indicated;

tube.

ma 6H6'twindiode can be used. Theserectifiers are' connected from conductor 132 to conductors 128 and" 122, respectively, and limit the input signal voltage on conductor 132 in a manner and for a purpose to be described more fully hereinafter.

The operation of the invention will now be described,

it being assumed for this purpose that the apparatus is installed on a pile fabric knitting machine as described herein .and that the main switches which supply current tothe'knitting machine and to' the needle spotter are closed, the knitting machine being idle, nevertheless, be-

causethe electromagnetic starting switch 104 is open.

Direct current being supplied to conductors 121- and 122 at this time, the Thyratron tube 120'has firedand' relay'109is energized, this relay being included in'the cathodeplatecircuit of the tube. Relay 106' is also in energized condition at this time, its circuit having been closed by relay 109;

When the operator actuates the switch S to start the machine, the plate circuit of the tube 120'is broken at 108, with the result that the tube is extinguished and relays 1Q9-and 106 are deenergized. The relay 106 has a relay'switch arm 107. The switch'S also closes a circuit for the electromagnet 104 at 1071', whereupon the:

magnet energizes and completes a locking circuit for itself at contact 105. Electromagnet 104 also'closes" the" switch contacts in the power line which supplies current to the motors such as 100, thereby'starting' the operation of the machine. After the'machine has been started'the operator may restore the switchS, or release it if it is a self restoring switch. The tube'120does not fire when its plate circuit is closed at 168 'becauseit now has a negative potential at its grid, generated by running of the machine. ative grid potential is generated will appear presently.

It will be recalled that the pickup device includes a magnetic circuit having an air'gap-throughjwhich fthe hooksof the needles such as 12 passsuccessively while The manner-in-which the neg-= the machine is running, flux being supplied to'this circuit by the permanent magnet 33; The" passageof -each needle through the gap --momentarily increases the' amount of flux, with the result that an alternating current is generated in coil 49 having a frequencywhich de'- pends on the rate at which the needles pass .the device-:-

If the cylinder speed is 105 ft. per minute and there'are-- l0 needles per inch the frequency will'be-210' cycles'peri" second. The coil 40 is then tuned approximately'tothat frequency by condenser 140.

The output of coil 40 is applied tothe grid circuit of tube 115, which operates as an eflicient amplifier; pro ducing a strong signal which is applied by wayof on=' denser 135 to the grid of tube 116.- The ARC. signal at'the grid of tube 116 is somewhat irregular'as regards the amplitude of successive cycles because of thefac'tthat each cycle is produced by a difierent needlefbut this irregularityis corrected at the following amplification stages.

The tube 116 has no grid bias and accordinglypasses nearly the maximum cathode plate current with" zero'- voltage at the grid. The positive half waves of the input signal do not much afiect the current flow through the tube, therefore, and are substantially eliminated as re- The negative gards any efiect they might have on the current andthe resulting voltage at the plate of the tube.

half Waves, however, are strongly amplified, producing:

large changes in voltage at the plate, which are transmitted through the condenser 136 to the grid oftube-1173 intheform of an A. C. signal of considerableamplituden Th -tube 1171155 a small g'rid'bias but is heavily overloaded. At each ilpositivehali; wave the cathode plate.-- current becomes substantially a maximum before the peak signal-voltage is reached-and-each negative half wave drives thegrid to' cutofffi The result is that the peaks of both the positive and negative half waves are eliminated as regards effecting 'changes in voltage-at== the plate of the'tubeg-anddt follows, '=therefore that the pulsating voltage at the' pIate of the tube' -has a square waveform and that-successive cycles are' of uniformamplitude independent of small -variations in the output of coil-40; The elimination-of the-positive half waves of signal voltage at tube -116 contributes to this result.

The voltage eha'rIges at.the plate oftube- 117 are "substantially in excess 0f. the uvolta'geacross the voltage regulator 119, which as previously -mentioned is volts, but the peak to peak volta ge of the A. 'C. signal produced at conductor "132 by coupling'condenser 137 is limited'to substantially l05 yolts by'theshunt circuits through the rectifiers 133 amb-134', as will. be explained i At each positive half wave-there is a path for the flow of current from-conductor 128- through' rectifier 133 to conductor 132,- but since as previously explained there is a positive potential of52z5' volts at conductor 128'110 current can fiowuntil the voltage at conductor 132 exceeds this value. At -e'ach 'positive-hal-f wave, therefore,

thelvoltage onconductor 132 rises until it reaches a 1 value of 52.5 voltsg whereupon current starts ;to flow through:- rectifier: i133; l'and' aszthis: rec ifier approximates 1 a short. circuit forrcurrentnin thisxdirectionno appreci-' able further rise inivoltage. carr occur:v

'I'he-rectifier13'4 limits the-ramplitude of the negative half. wavesz.of':signal' voltage -on conductor 132"in a 1 similar mannenxaswit 'providesia path' for current-flow from conductor 132itorconductort122;l The latter con= ductor has a negativexpotential of 52.5 .volts with'respectto.ground so thatno currentzcan flow. until-the voltage on conductor 13,2ifalls below thisvalue. The conductor: 122 then becomesr-positive with respectto conductor 132, .current startstoflowgand further fall in potential at conductor 1321is .prevented'.

Continuing. with-the explanation,::each. negative hal-f' wave of signal voltagemnconductor. 132-iproduces a fiow 131. vThecondenserzis :chaigedLeach'time to a constant ,of .current thIOughJthe diode1118to' charge thezcondenser voltage which is approximately525 volts but cannot ex ceed'thatvalue' vbecause'ofthe'ilimit imposed onthe volt- 1 age at conductor 1321bythe circuit .throughthe rectifier 134. The chargingiofscondenser.131*places a negative potential on the grid of the Thyratron which is equal to thechargeonithe condenser, 'or:52.5 volts'. 1 The cath- Ode :of: the tube has: a negative-potential of somewhere around 28 volts so'that the grid has a negative potential A? with respect tothe cathode which is morethan sufficient to prevent thetube from firing.

At :each positive half wave the condenser 131 partially discharges through the resistor 130, but not enough to permit the Thyratron -120 to fire; The resistancevalue' of resistorl30iis so related to the capacity of the condenser 131 andthe length'of the'time intervals during whichxit dischargesthat at the end of each discharging 1 period the potential on the grid of'tube 120 is still sum ciently negative with respect to the cathode-to prevent .the tube fromfiring." It may be sta ed, however, that each: time the condenser discharges the. greater part of the difference -between the'gridjand cathode potentials is potential-.farenough to cause thetube to fire.

determinesrthe potential on the cathode of the tube.

The:machine is nowoperating'inthe normal manner to .knitipilefabric, all of its .needles presumably being uiring any attention from the operator.

Assuming now that thefhook on one. of the needles certain distance beyond the' pickup device. I ping of the machine maybe sufficient to attract the ate V r I tentionof the operator but if desired a' special signal'such again'by actuation of the' startingr switch Su in good condition. The operator has released the start- 1 ingswitch S, thus supplying plate voltage to the Thyra tron 120, but the tube is prevented from firing as just explained-and the machine continues to'run without re J breaks 01f, when this needle passes the pole piece 34 of a the pickup device the flux in the magnetic circuit is not altered appreciably and one cycle is omitted from the A. C..output' of the coil 40. .The corresponding cycle in the signal voltage at conductor 132 is of course omitted'also and the condenser 131,. instead of getting its reg ular charge 'at'that point, continues to discharge through the resistor 130. The negative potential at the grid of the Thyratron 126 then, very quickly falls low enough so that the tube can fire.

When the tube 120 fires as the result of thedetection of a broken needle as explained above, the relay Hi9 is energized, and closes'af circuitifor relay 1 06. Upon" energizing, relay N6 breaks'the locking circuit of the electromagnetic starting switch 104 at contact 107 and to' prov'idea magnetic circuit including an air :gap and another part is provided. with an array'of operated hooked knitting needles posit oned with referenceto'the gap 501 that-the hooks of the needles pass successively there I through during the operation or" said machine, 'a magnet included in said circuit to'provide a flow of.magnetic flux across said gap, means for starting 'said machine a coil inductively related to said magnetic circuit and in which alternating current is'generated by the passageof the hooks of. said needles through the gap'fmeans for maintaining said machine in operation independent of said starting means, and means responsive to a momen tary interruption in said alternating .current produ'ced'by the passage of a brokenneedle having no hookto' pass theswitch opens the motor circuits to stop themachine. j

know where to, look forthe broken needle, that is, a

as15tl may be provided. The replacement of the broken needle by a new one takes only a half minute or so, and when the change is completed the machine is started up There will be some overrun but the amount is approximate-1y the same each time sothat the operator will;

The stop "The" manner in which the machine is stoppedwhen "the latch of a needle becomes stuck willbe'readily'unde'r 'stood' in view'of the foregoing. When the stuck latch needle passes the pickup device the latch of theneedle momentarily engages the *feeler' member 52, thereby grounding the terminal and the, grid of tube 129.

This causes the tube to fire, whereby relay ltl9 'is energized to stop the machine as previously explained;

While certain values of resistance, voltage, etc. have been mentioned herein it will be understood that these values have been given by way of example, to facilitate the explanation, and that the invention is not limited thereto. Nor is it to be limited to the exact mechanical construction and electrical circuit arrangement shown and described herein.' 'Modification may be made withprotection therefore for all forms of the invention that come within the scopeof the appended claims.

We claim:

through said gap, for'disabling'said maintainingmeans' and thereby stop said machine.

4. A power operated knitting machine having rela-' tively movable parts certain ofwhich? are arranged to' provide a magnetic circuit having an air gap and another :part has an array of hooked knittin g n eedles positioned I 'whereby the hooks of the needles pass through the gap successively during theoperation of the machine, a magnetfor producing magnetic flux in said'circuit, a coil" inductively related to said circuit in whichithe needles passing through said air gap generate alternating current by varying the amount of said flux, means forampl fying said alternating current, a'condenser means utilizing each1 alternate half wave 'of the amplified alternatmg current to charge said condenser tofaconstant value, a

shunt circuit through which said condenserpartially dis-- charges to. a predetermined minimum value after each charge-and continues to discharge below said minimum hooks of the needles of the knittingmachine-pass sue e in" the principles of the invention and we desire to secure 1. In a knitting machine having a frame and framesupported relatively stationary parts and a'power operinductively related to said magnetic circuit and in'which each passing needle generates a cycle of alternating cur-f rent bychanging the amount of flux in said circuit, elec- 'tric circuit meansfor said coil and connected apparatus forspotting a broken needle by detecting a'missing cycle,

and meanscontrolled by said apparatus'for stopping'the cylinder upon detection of a missing'cycle. 2. In a knitting machine having relatively movable 7 parts certain of which are arranged'to provide a magnetic circuit including an air gap and another part includes a' cylinder equipped with hooked knitting needles mounted so that the hooks of the needles pass successively through the gap during the operation of said machine, .a magnet included in said'circuit to provide a flow of magnetic flux across said gap," electrical means for starting said machine, a coil inductively related to said magnetic cir- 7 cuit and in which alternating current is generated byth e unless the next alternation is induced 'by thehook of another needle passing through-the gap; and means controlled in accordance with the value of the charge on said condenser to stop the machine ifrthe charge falls'below a value which is lower than'the said minimum value.

5. In a. knitting machine having hooked needles mount-- ed for movement in a knitting operation certain parts 1 of said knitting machine being arranged to provide a;

magnetic circuit having an air 'gap through which the relatedto said circuit in which the needles passing through said air gap generate alternating current by varying the amountof said flux, means for amplifying sflidalternau ing current, a condenser; means utilizing each alternate half wave of the amplified alternating current to charge said condenser to a constant value, a shunt circuit through which said condenser partially discharges to a predeterg mined. minimum value after each charge, a space discharge device maintained in nonconductivecondition by the charge on said condenser, there'being a conductive connection between the grid of said device and the nega-.

tive. terminal of said condenser, adjustable bias means' adapting said device to fire, said charge falls substantially below said minimum 'value, a'relay connected for. energization responsive to' firing of said device, and means: responsive to energization of said relay to stop said 1 machine. e

', 6. Amagnetic pickup devicefor spotting broken-needles in a circular knitting machine, said machine being adapted: to be maintained in power operationby an uninterrupted alternating current, said knitting machine having rela-: tively moving parts, one of which is provided'with hooked i needles andrcertain of thelother parts'having-rneans. pro-" viding a magnetic circuit including a pole piece located adjacent the path of the needles'jof'said rnachine anda magnet adapted to utilize the hooks of the needles t'o' complete said circuit when the hooks of successive regularly spaced needles pass said pole piece during the operation of said machine, and a winding inductively related to said circuit and in which an alternating current is generated due to the varying flux in the magnetic circuit as successive hooks pass said pole piece whereby a missing book of one of said needles will provide an interruption in the alternations, and connection to pass the alternating current to maintain the operation of the machine.

7. A magnetic pickup device for spotting broken hooked needles in a circular knitting machine having a sinker cam ring and other parts of magnetic material, said device comprising a base adapted to be mounted on the sinker cam ring of said machine, and said other parts of magnetic material being arranged to provide a flux path, a magnet supported on said base with one pole in contact with said ring, said ring being magnetically connected with the needles of said machine by said other parts, a pole piece supported on said base and connected through said magnetic material to the other pole of said magnet, said pole piece having its extremity disposed adjacent the path in which the hooks of said needles travel during the operation of said machine, and a coil surrounding said pole piece in which an alternating current is generated by the passage of said hooked needles.

8. A magnetic pickup as claimed in claim 7, including a member supported on said base and having an aligning surface slidably engaged by the hooks of said needles as they approach and pass said pole piece.

9. In a knitting machine, a motor for driving said machine, an electromagnetic switch for starting said motor, a manually operated switch for closing an energizing circuit for said starting switch, a locking circuit for said starting switch to maintain the same operated independent of said manually operated switch, a relay for opening said locking circuit, apparatus for detecting a defective needle as it passes a certain point in its path during operation of the machine, a second relay energized by said apparatus upon the detection of a defective needle, and a circuit completed by energizing said second relay for energizing said first relay to break said locking circuit and stop said machine.

10. A knitting machine having relatively movable parts one of which is provided with knitting needles adapted to be actuated in a knitting operation, means including a magnet mounted to another of said parts and providing a magnetic circuit having an air gap through which portions of the needles pass successively during the operation of the machine, a coil inductively related to said magnetic circuit and in which each passing needle generates a cycle of alternating current by changing the amount of flux in said magnetic circuit, and an output circuit for the coil with electrically responsive apparatus for spotting a missing needle portion by detecting a missing cycle.

11. In a knitting machine having a multiplicity of knitting needles mounted in a part of the machine which moves with respect to another part of the machine, a magnet and means forming parts of the machine shaped to provide a magnetic flux path and an open air gap through which successively pass portions of each of the needles during the operation of the machine, a coil having an output circuit and inductively related to the magnetic flux path in which each successive needle portion passing through the gap changes the magnetic flux and generates a cycle of alternating current in said output circuit, apparatus in said output circuit responsive to a missing cycle coincident with the failure of a needle portion to pass through the gap, and means controlled by said apparatus responsive to the missing cycle to stop the machine.

12. In a knitting machine with a movable part having a succession of latch needles in evenly spaced arrangement, a magnetic flux circuit completing device with an air gap positioned to permit passage of at least a portion of each needle through the gap, means including a power unit for starting and running the machine, and an electrical control apparatus for said power unit including as a portion thereof a control circuit for alternating current, a coil in said control circuit inductively related to the magnetic circuit whereby the passage of needles through the gap causes the induction of an alternating current in said control circuit, said control apparatus also including means requiring an uninterrupted cycle of alternations in the current coinciding with the movement of successive needles through the gap whereby a failure of a portion of a needle to pass through the gap will stop the machine.

13. The knitting machine of claim 12 wherein the control apparatus requiring an uninterrupted cycle of alternations includes a relay switch in a circuit for the power unit and a grid controlled space discharge tube having an anode circuit for control of the relay switch, said tube having a grid circuit supplied by said alternating current whereby upon an occurrence of an interrupted cycle in said grid circuit the anode circuit will change the setting of the relay switch.

14. The knitting machine of claim 12 wherein the control apparatus requiring uninterrupted alternations includes a relay switch in the circuit for the power unit and a grid control space discharge tube having an anode circuit for control of the relay switch, the knitting machine also having a feeler positioned to contact closed latches of the needles at a point where latches of the needles are normally open, and a circuit for the feeler to connect it with the grid of the tube whereby to ground the grid through a closed latch and thereby interrupt the alternations.

15. In an apparatus of the character described, an electrical machine control circuit in which electric impulses at minimum time intervals are necessary to prevent a stoppage of the machine controlled by said circuit, a machine with relatively movable parts electrically op erable and connected for control by said control circuit, certain of said relatively movable parts in the machine being equipped with a magnetically permeable flux circuit having a gap, working elements carried by another of said parts and mounted in evenly spaced relation for passage through said gap in the relative movement of the parts, a coil inductively related to said magnetic flux circuit and connected with the control circuit for feed of electric impulses at time intervals corresponding with the passage of said elements through the gap whereby a missing element will cause an elongated time interval between impulses, and power means for operating the relatively movable parts at a speed to move the elements through the gap at time intervals more frequent than said minimum time intervals when there are no missing elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,016,208 Locke et a1. Oct. 1, 1935 2,257,037 Crawford Sept. 23, 1941 2,389,688 Ruth Nov. 27, 1945 2,534,584 Epstein Dec. 19, 1950 FOREIGN PATENTS 493,818 Germany Mar. 14, 1930 991,515 France June 20, 1951 

